Gate, leaf and method for controlling water levels in a body of water

ABSTRACT

A gate, leaf, and method for controlling water levels in a body of water. The gate comprises a moveable barrier (which may be a leaf), a restoring device such as a spring, and a profile. The barrier automatically opens or closes an amount to allow less or more water through as a result of changes in the water pressure in the upstream body of water. This helps maintain a water level in the upstream body of water. The profile disturbs the flow of water through the gate to influence the water pressure on the barrier. The profile may help provide a more linear curve for the water moment on the barrier across the range of barrier positions. A more linear curve for the water moment may help maintain equilibrium with the restoring moment across the range of barrier positions. The method comprises disturbing the flow of water over a barrier to redistribute the pressures of the water on the barrier.

FIELD

The present disclosure relates to the control of water levels in bodies of water.

BACKGROUND

A spillway regulates the flow of water out of an upstream body of water. This, in turn, helps regulate the water level in the upstream body of water. There are generally two types of spillways: gated spillways and ungated spillways.

An ungated spillway comprises a fixed structure. Water flows out of the upstream body of water by overtopping or passing through the structure. Since there are little to no moving parts, ungated spillways (as compared to gated spillways) are less likely to become obstructed by debris, are less prone to operator error and equipment failure, and have fewer operational and maintenance costs. However, the discharge capacity of ungated spillways is limited.

Gated spillways offer greater control of downstream and upstream water levels than ungated spillways and the potential for increased discharge capacity. In a gated spillway, the gate is adjusted to change the rate at which water is allowed to flow out from the spillway. A gated spillway can better accommodate the passage of irregular and high volumes of water flowing into a body of water as would be experienced in a storm event or flood.

A stop log spillway is an example of a gated spillway. The barrier is formed by stacking large stop logs one on top of another across the mouth of the spillway in stop log bays. The stop logs are held in place by vertical guides (also referred to as gains) formed in piers on both sides of the spillway. The wall of stop logs inhibits the flow of at least some of the water out of the spillway thereby setting the water level within the upstream body of water. The height of the wall of stop logs may be altered by manually adding or removing stop logs in the vertical channels from above. A stop log lifter is used to raise and lower the logs in those vertical guides. Since stop logs are a fixed height, the height of the wall may only be changed by discreet increments corresponding to the height of the logs themselves. This limits the accuracy to which upstream water levels may be regulated.

There are a number of challenges with stop log spillways. Stop logs must be manually added or removed from the spillway to respond to rising or falling water levels in the upstream body of water. In some locations, regulators require an operator of a spillway to maintain the upstream water levels within a narrow band of 150 millimeters or even less. Accordingly, a stop log spillway may need to be visited frequently by the operators, and often under adverse weather conditions. This can prove hazardous and costly since a spillway may be located in a remote area which is not accessible by road, and may only be accessible by boat, helicopter, or float plane. Furthermore, stop logs can be 18 feet or more in length, making them heavy and difficult to handle. Additionally, many stop log spillways are quite old, and therefor equipped with old stop log lifters called crab winches (which are sometimes well over 50 years old). This impacts the reliability of this type of spillway and the safety of the operators using the equipment.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a cross-section side view of a gate for controlling the level of water in a body of water according to an embodiment of the present disclosure

FIG. 2 shows a plan top view of a gate for controlling the level of water in a body of water according to another embodiment of the present disclosure.

FIG. 3 shows a transparent front view of the gate shown in FIG. 2, taken along cut lines A-A.

FIG. 4 shows a cross-section side view of a gate for controlling the level of water in a body of water according to another embodiment of the present disclosure.

FIG. 5 shows a graph plotting the angle of a leaf against the moment of water acting on that leaf for a gate comprising a conventional flat leaf, and a gate comprising a leaf and a profile according to the present disclosure.

DETAILED DESCRIPTION

In an embodiment, a gate comprising a moveable leaf and a profile are positioned within a spillway to automatically and more accurately control the rate at which water is allowed through the spillway to control the water level in the upstream body of water. The leaf may be hinged along its bottom horizontal axis and biased towards a closed position with a restoring device such as a spring. The water exerts an opening moment on the leaf, and the restoring device exerts a closing moment on the leaf. At a particular angular position, the opening and closing moments are balanced. Depending on the angular position, a certain amount of water may be allowed to pass over the top of the leaf. The angular position at a particular water pressure may be commensurate with the amount of water required to be released to maintain or achieve a particular band of water levels within the upstream body of water. The profile may disturb the flow of water over the leaf to alter/redistribute the pressure of the water on the leaf from what would have been experienced by a leaf without a profile. The profile may help provide a more linear curve for the water moment on the leaf across the range of leaf positions. In an embodiment, the profile may be a trough in the surface of the leaf.

FIG. 1 shows a cross-section side view of a gate 100 for controlling the water level in a body of water according to an embodiment of the present disclosure. The gate 100 comprises a leaf 102 (also referred to herein as a flap). The leaf may be any form of barrier or wall. The leaf 102 has a bottom end 104, a top end 106, an upstream face 108, and a downstream face 110. The bottom end 104 is attached by a hinge 112 across the width of the leaf 102 to a base plate 114. The base plate 114 is a shoe having a C-shaped cross-section for fitting over a top stop log in an existing stop log spillway.

The hinge 108 permits the leaf 102 to pivot on a horizontal axis on its bottom end 104 between a first position and a second position. The first position may be a closed position 116 wherein the plane of the upstream face 108 of the leaf 102 is closer to vertical. The second position may be an open position 118 wherein the plane of the upstream face 108 of the leaf 102 is closer to horizontal. In the closed position 116, the plane of the upstream face 108 may be as much as 75 degrees from horizontal. In the open position 116, the plane of the upstream face 108 may be as little as 15 degrees from horizontal. In an embodiment, the closed position 116 and the open position 118 may be at any degree of rotation of the leaf 102, so long as the angle of the plane of the leaf 102 relative to the ground is greater when the leaf is in the closed position 116.

The gate 100 also comprises a restoring device 120 for biasing the leaf 102 in the direction of the closed position 116. The restoring device 120 may be one or more springs. The springs may be torsion springs. A spring 120 may encircle the shaft of the hinge 112, with one end of the spring 120 applying a rotation force against the leaf 120, and the other end of the spring 120 applying an equal but opposite rotational force against the sill/base plate 114. The springs may be substantially linear throughout their ranges of motion such that the force each spring provides increases linearly with the winding of the spring. The springs may be wound prior to installation to achieve the required pre-tension. The springs may be stainless steel so as not to corrode from long term submersion in water. The hinge 112 may comprise self-lubricating bearings intended for operation in water. Nylon spring sleeves may be used to minimize the friction and hysteresis between the springs, hinge 112, and other elements of the gate 100. The restoring device 120 may be any device which provides an increasing amount of force when moved in a particular direction, and which can allow the leaf 102 to move through a range of rotation (such as 70 degrees). The restoring device may be a counterweight configured to bias the leaf 102 in the direction of the closed position 116.

The gate 100 is positioned within the spillway such that the leaf 102 pivots in a downstream direction of the spillway. The elevation of the gate 100 may be selected so that the desired water level in the upstream body of water is near, but below, the top end 106 of the leaf 102 when the leaf is in the closed position 116. The elevation of the gate 100 may be adjusted be adding or removing stop logs underneath the gate 100. A spillway may be retrofitted with the gate 100 by removing some of the top-most stop logs, then fitting the base plate 114 over and securing to the remaining stop logs. In this way, the gate 100 replaces the top two or three stop logs in an existing spillway. The gate 100 may be easily removed to permit re-installation of stop logs, such as during a flood or in winter months when the body of water freezes.

During operation, the gate 100 automatically helps maintain a relatively constant water level within the upstream body of water without additional power or operator intervention. It accomplishes this through automatically changing the angular position of the leaf 102 (i.e. further opening or closing the leaf) according to the amount of pressure exerted by the water in the upstream body of water on the leaf 102. The upstream body of water exerts an opening force on the leaf, and the restoring device 120 exerts a closing force on the leaf. In this way, the force exerted by the upstream body of water is balanced with the force exerted by the restoring device 120 at a particular angular position of the leaf, and at that angular position the leaf allows a sufficient amount of water to pass through the gate to maintain or achieve a desired water level in the upstream body of water.

The angular position of the leaf 102 determines the rate at which water flows out of the upstream body of water through the gate 100. Pivoting towards an open position 118 lowers the elevation of the top edge 106 relative to the water level in the upstream body of water allowing a higher flow rate of water through the gate 100. Pivoting towards the closed position 116 raises the elevation of the top edge 106 relative to the water level in the upstream body of water reducing the flow rate of water through the gate 100.

When the water level in the upstream body of water rises, the additional force exerted by the water on the leaf causes the leaf to further open thereby allowing more water to escape over the top of the leaf. The leaf continues to open until the moment exerted by the restoring device 120 on the leaf 102 is balanced with the moment exerted by the water on the leaf 102. When the water pressure in the upstream body of water falls, the greater moment exerted by the restoring device 120 causes the leaf 102 to move towards the closed position until the opening and closing forces are once again balanced. Moving towards the closed position reduces the amount of water that can escape over the top of the leaf 102. The pressure exerted by the water on the leaf at a point in time may correspond to the rate at which water is passing over the gate in combination with the elevation of the water in the upstream body of water at that point in time. For example, the pressure exerted by the water on the leaf 102 may be greater when water is already flowing over the leaf 102, than when it is not, for a given water level in the upstream body of water.

The gate 100 may seek an equilibrium state such that it is at an intermediate position between the open position 118 and the closed position 116. The gate may be in an equilibrium state when the water level in the upstream body of water is around a threshold level. The threshold level may be within the desired band of water levels for the upstream body of water. In an embodiment, the gate 100 may maintain an upstream water level within a band of 100 millimeters or less.

The angular position of the leaf 102 may depend on the flow rate of water into the upstream body of water (i.e. the rate of accumulation of water in the upstream body of water). For example, if the rate at which water accumulates in the upstream body of water increases, the leaf 102 may automatically rotate a certain amount in the direction of the open position 118 to increase the rate at which water is allowed by the leaf 102 to flow out of the upstream body of water via the gate 100. Similarly, if the rate at which water accumulates in the upstream body of water decreases, the leaf 102 may automatically rotate in the direction of the closed position 116 to decrease the rate at which the leaf 102 allows water to flow out of the upstream body of water. In this way, the gate 100 may help automatically match the water flow rate out of the upstream body of water with the water accumulation rate in the upstream body of water.

The leaf 102 may comprise a profile 140 on its upstream face 108. The profile may be a trough. The profile may extend from the surface of the upstream face 108 towards the downstream face 110. The profile may comprise a single concave surface in the shape of a bowl. Or the profile may be formed of two or more surfaces. For example, as shown in FIG. 1, the profile 140 is a trough comprising two side walls 142, 144, and a base 146. The trough may extend the entire length of the leaf 102 from cheek plate to cheek plate, or only a portion of the leaf 102. The width of the trough at its widest point (which may be its mouth) may be one third of the total width of the leaf 102. The total width of the leaf (the distance between the bottom end 104 and the top end 106) may vary depending on the site conditions. The leaf may have an overall width between 1 and 4 feet. Each side wall 142, 144 may be at an angle of forty-five degrees relative to the upstream face 108. Alternatively, the side walls 142, 144 may each be at an alternate angle of up to 90 degrees to the upstream face 108. The plane of the base 146 may be parallel to the plane of the upstream face 108. The trough may be closer to the top end 106 than the bottom end 104 of the leaf 102. The depth of the trough 140 may be one-third the width, but this may vary depending on the site conditions.

In an embodiment, the profile may be formed by the leaf 102, itself, or in the upstream face 108 of the leaf. Alternatively, the profile may be a separate element from the leaf 102 but disposed on or proximate to the leaf 102, such as on the upstream face 108 of the leaf, or on the top end of the leaf 102. The profile may be any shape or comprise any texture which is sufficient to one or more of the following: influence the pressure distribution of the water on the leaf for a particular gate angle, and disturb the flow of water over the leaf 102 by an amount proportional to the velocity of the water flowing over the leaf 102 so as to influence the water pressure on the leaf to achieve a particular desired moment against the leaf 102. For example, the profile may be a combination of one or more of a recess, cavity, protrusion, deformation, and curve.

The water pressure distribution on the leaf 102 is partly dependent on the accelerating flow field of the water over the leaf 102. Using the profile 140 to redistribute the water pressure on the leaf may help provide a more linear increase in the moment curve representing the water pressure acting on the leaf 102 as the leaf moves from a first position to a second position. The first position may be a closed position, and the second position may be an open positon. The redistribution of the water pressure is with respect to an original water pressure that a similar conventional leaf, but without a profile, would experience. In an embodiment, the profile is configured to disturb the flow of water flowing over the top end 106 of the leaf 102. In an embodiment, the profile is configured to disturb the water that is flowing from the bottom end 108 to the top end 106 of the leaf 102. In an embodiment, there may be a plurality of profiles positioned at different locations on the same leaf 102. In an embodiment, the profile provides a select distribution of water pressure on the leaf in response to the leaf moving a select amount towards the open position 118. The select distribution of water pressure may be more favourable in that it provides a more linear increase in the moment exerted by the water on the leaf 102 across the range of angular positions of the leaf 102 from a closed position 116 to an open position 118. In an embodiment, the same profile allows the leaf 102 to respond, thereby moving it towards the closed position 118. In an embodiment, the restoring device 120 and the profile 140 are configured to work in tandem to cause the leaf 102 to achieve a particular water discharge rate to gate angular position relationship. In an embodiment, the hydrodynamic pressures acting on the leaf 102 are balanced with the forces exerted on the leaf 102 by the restoring device 140 over a large range of leaf angular positions.

In an embodiment, the profile 140 comprises a curved surface which influences the pressure distribution of the water on the leaf 102 such that the moment varies constantly across the range of angular positions of the leaf. The curved surface may comprise a first section which curls towards the downstream face 110, and a second section which curls towards the upstream face 108. The first section may be upstream of the second section.

Through the use of a restoring device 120 which conserves energy, additional power is not required to operate the gate 100. Avoiding the need to provide additional power to control a spillway is important. Spillways may be located in remote areas without electricity or other energy sources. Even if sufficient electricity could be provided to power a gate (including through electricity generation by the spillway itself), the cost of procuring, installing, and maintaining power transmission/generation equipment, and gate devices which use that power, could be prohibitive, especially in remote locations. Furthermore, if the systems providing/using the power were to fail, it may take a period of time to first discover that failure and even further time to remedy the failure. Having an improperly controlled spillway for even a brief period of time can have significant consequences. For example, higher than desired water levels can erode shorelines, displace wildlife, harm ecological systems and result in regulatory charges and fines.

Having the leaf 102 pivot on its horizontal axis proximate to the bottom end 104 helps reduce the likelihood of debris (such as tree limbs, ice, and sediment) from becoming stuck in/clogging the gate 100 and interfering with its normal operation. This is because the leaf 102 is more likely to fold down out of the way as a result of the weight of debris, allowing the debris to freely spill over the top 106 of the leaf 102, thereby reducing the risk of it becoming ensnared in a structure above the leaf 102.

FIG. 2 shows a plan top view of a gate 200 similar to the gate 100 of FIG. 1 in accordance with an embodiment of the present disclosure. The gate 200 is positioned between piers 252, 254 defining a water passage 250. The gate 200 is in a substantially closed position. The base plate 214 of the gate 200 extends beyond the width of the water passage 250 such that the ends of the gate 200 fit into slots in the piers 252, 254. Water flows through the water passage 250 in the downstream direction Z. Similar to the gate 100 of FIG. 1, the gate 200 comprises a leaf 202, a hinge 212, a base plate 214, and a restoring device 220. FIG. 2 also shows the gate 200 comprising cheek plates 222, 224. The cheek plates 222, 224 provide a smooth surface at the sides of the water passage 250 against which the leaf 202 may interface. This smooth surface provides a better seal for the leaf 202 which inhibits water from leaking around the leaf 202 at its sides.

During operation, the force of water exerted by the upstream body of water pushing in direction Z overcomes the opposition force of the restoring device 120 to cause the leaf 202 to pivot about the hinge 212 on its horizontal axis so the top of the leaf 202 travels downstream in the direction of the flow of the water Z.

FIG. 3 shows a transparent front view of the gate 200 taken along cut lines A-A in FIG. 2. As shown in FIG. 3, the profile 240 in the upstream face 208 of the leaf 202 is in the shape of a trough. The trough comprises sides 242, 244 and a base 246.

FIG. 4 shows a cross-section side view of another embodiment of a gate 400 similar to gates 100, 200 of FIGS. 1, 2, and 3, but as would be taken along cut-lines C-C of FIG. 3. The gate 400 comprises a cheek plate 424, and a side seal 428 which interfaces with the cheek plate 424 to inhibit water from escaping therebetween. The cheek plate 424 fits against a pier at the side of the spillway to provide a smooth surface for the side seal 428 to pass over. The gate 400 also comprises a damper 430 to resist sudden movement of the gate 400. The damper 430 may help inhibit the gate from making cyclical movements (such a fluttering) due to wave action in the upstream body of water contacting the leaf 402. The damper 430 may comprise a damping cylinder 432 such as a pneumatic or hydraulic cylinder. The damping cylinder 432 is affixed at one end to the base plate 414, and affixed at the other end to the leaf 402. The damping cylinder 432 contracts and expands with the opening and closing of the leaf 402 to slow the rate at which that motion occurs. The damping cylinder 432 may be tuned to dampen certain motions of the leaf 402 from waves having a particular frequency and/or amplitude. The gate 400 also comprises a spring seal 434 which inhibits the flow of water between the sill defined by the base plate 414, and the bottom of the leaf 402. One end of the spring seal 434 may be affixed to the base plate 414 with the other end of the spring seal 434 allowed to freely slide over the lip of the leaf 402 as the leaf 402 rotates.

The self-actuated/self-adjusting function of the gate of the present disclosure helps automatically regulate water flow and thereby control water levels in bodies of water without operator monitoring and/or intervention. This provides some of the advantages of an ungated spillway together with the enhanced water control advantages of a gated spillway. This can help decrease the number of operator visits to a spillway to manipulate stop logs or other water level control devices and improve operator safety.

FIG. 5 shows a representative graph 500 plotting the angle of a leaf 502 (in degrees from horizontal) against the moment of water acting on that leaf 504 (in newton meters) for each of a conventional flat leaf 506 and a leaf comprising a profile 508 according to the present disclosure. As shown in plot 506, when a conventional flat leaf opens past a certain point (in this case, 30 degrees), the downward force of the water on the leaf changes so that it no longer follows the linear moment curve from gate angles 70 to 30 degrees. This change in water force resulting in a non-linear curve may be in part due to both the increase in velocity, and the momentum of the water, as more water is allowed to flow through the gate at a given time. It may also be partly due to the static pressure exerted by the water on the leaf. As the leaf opens and more water rushes through, the column of water above the leaf increases. Restoring devices such as springs, however, typically have a more linear force curve.

As shown in plot 508, the profile 140 influences the moment of the water on the leaf 102 across a range of leaf angles. The profile 140 may help make the water moment curve more linear across the range of leaf angles (although the profile 140 may not necessarily reduce the total moment exerted by the water that a conventional flat leaf would have experienced at any particular leaf angle). It may be desirable to have the moment curves of the water and the restoring device substantially correspond. This may allow for a more progressive opening of the gate. Providing a more linear water moment curve may help with using restoring devices (such as springs) that also have linear force curves. Using relatively common restoring devices (such as springs) may help simplify the design and control the cost of the gate.

A gate in accordance with an embodiment of the present disclosure may not be limited to spillway applications. The gate may be used in place of flashboards on the crest of a weir, helping to increase water storage and head within the upstream body of water for power production, but responding to storm events without operator intervention (enhancing dam safety) and without the requirement for electric power. 

We claim:
 1. A gate for controlling a flow of water from a body, comprising: a leaf configured to be moved between an open position and a closed position; a restoring device configured to bias the leaf towards the closed position; and a profile configured to disturb the flow of water through the gate for influencing the water pressure on the leaf.
 2. The gate of claim 1, wherein the profile is a trough.
 3. The gate of claim 2, wherein an upstream surface of the leaf defines the trough.
 4. The gate of claim 1, wherein the restoring device is a spring.
 5. The gate of claim 1, wherein the leaf is hinged at a lower end for rotating about a horizontal axis between the open position and the closed position.
 6. The gate of claim 1, further comprising a base plate connected to the leaf, the base plate for fitting over an existing stop log in a spillway.
 7. The gate of claim 1, wherein the profile is configured to influence the pressure distribution of the water on the leaf according to the rate at which water flows over the leaf.
 8. The gate of claim 1, wherein the profile is configured to cause the moment of the water on the leaf to increase substantially linearly from a first position to a second position.
 9. The gate of claim 5, wherein the profile and the restoring device are configured to cause the leaf to automatically rotate to an angular position which permits a rate of water flow through the gate that is proportional to the rate at which water is accumulating in the body.
 10. The gate of claim 1, wherein the profile comprises a curved surface which influences the pressure distribution of the water on the leaf such that the moment varies constantly across the range of angular positions of the leaf.
 11. A method for controlling a flow of water from a body, comprising providing a leaf biased towards a closed position to inhibit the flow of water from the body; and influencing the pressures of the water on the leaf to provide a substantially linear increase in the moment of the water on the leaf in response to the leaf moving towards an open position.
 12. The method of claim 11, comprising disturbing the flow of water over the leaf to influence the pressures of the water on the leaf.
 13. A method for controlling a water level in an upstream body of water, comprising allowing for continuous adjustment of the flow of water out of the upstream body of water at the same rate as water accumulates in the upstream body of water.
 14. A method for maintaining a water level, comprising automatically allowing a top edge of a barrier retaining an upstream body of water to lower in response to an increase in the rate of water accumulating in the body.
 15. A method for converting a gated stop log spillway, comprising removing one or more stop logs from the spillway, providing a gate comprising a leaf, the lower end of the leaf attached to a base plate with a hinge, the leaf biased towards a closed position with a spring disposed about the hinge; and affixing the base plate to the top of the remaining stop logs in the spillway.
 16. The method of claim 15, wherein the base plate comprises a C-shaped shoe, and affixing the base plate comprises fitting the shoe over at least the top stop log.
 17. A leaf for a gate to control a water level in a body of water, the leaf comprising a profile configured to disturb the flow of water passing over the leaf to influence the water pressure on the leaf.
 18. The leaf of claim 17, wherein the profile is a trough. 